Over the past several years there has been a large growth in the number of different types of telephones which are purchased by telephone customers for use in their homes and offices. These phones, because they are purchased by the telephone user, are normally identified as being Customer Provided Equipment (CPE) telephones.
These CPE telephones are required to meet a ringer-equivalence standard as specified in Part 68 of the FCC Rules. The purpose of the ringer-equivalence standard is to provide a termination at the end of a subscriber loop that will enable telephone repair personnel to distinguish between an open conductor condition of a subscriber loop and a properly terminated subscriber loop. The ability to make this distinction can prevent an unnecessary dispatch of a repair person.
More specifically, a subscriber loop which has no faults and which is terminated with a telephone which meets the FCC rules will have a specific ac impedance. The absence of this specific ac impedance strongly suggests that one or both of the conductors, the tip conductor or the ring conductor of the subscriber loop has an open condition. Clearly, the ability to accurately detect the presence of a telephone at the end of a subscriber loop is necessary when a subscriber's loop is terminated with a CPE telephone.
It is estimated that approximately 1.4 million of the telephones in use today have ringer-like terminations that do not conform to the ringer-equivalence standard of the FCC Rules and are not currently detectable by existing test methods. Because of the proliferation of undetectable CPE telephones, telephone companies must manually screen customer trouble reports that indicate an open loop condition. This screening usually includes attempts to call the subscriber to help isolate customer provided equipment type of trouble reports. It is estimated that CPE telephones which do not satisfy the FCC termination Rule causes an unnecessary test expense of approximately 25 million dollars per year. Clearly, a need exists for a method of distinguishing between an open conductor and a properly terminated subscriber loop.